This application is based on and claims the benefit of German Patent Application No. 200 16 527.5 filed Sep. 23, 2000, which is incorporated by reference herein.
The invention relates to an electric installation cable, in which the insulated wires forming the core and serving to conduct electricity are bound together as one unit.
A wide variety of such cables have been used for many years anywhere an electric current is required. In this context the cables have been used in all types of buildings and for supplying power to stationary and movable electric machines. Cables usually have three or more cores, one of which normally functions as an insulated ground wire. As long as the cables are used exclusively to transfer electricity, no problems occur with appropriate handling. However, the use of such cables to transfer high frequency telecommunications signals and data in today""s ever-advancing technology is limited, since their impedence is too irregular for such purposes.
The task of the present invention is therefore to develop the cable described above so that it is also suitable without limitation for the undisturbed transfer of telecommunications signals.
This task is solved in accordance with the present invention in that
the unit comprises four core wires bound together to form a star-quad,
the core wires are shielded by a plastic film coated on both sides with aluminum,
tinned copper wires functioning as ground wires are bound around the shield and
a coat of insulation material is placed over the tinned copper wires.
Such a cable is designed symmetrically in the form of a star-quad. It thus has a regular cable impedance of, for example, 100 ohms at 1 MHz. Because of the symmetry of the cable, high frequency signals can be transferred without trouble by two cable circuits arranged at right angles to one another. Also, due to the very regular cable impedance, there are no significant signal reflections. The shield surrounding the tinned copper wiresxe2x80x94hereinafter referred to as a xe2x80x9cground wirexe2x80x9dxe2x80x94also provides excellent shielding for the cable, even for higher frequencies in the 1 MHz range. The core wires are therefore protected against the influence of outside electromagnetic fields and no interference is given off from the cable. The ground wire surrounding all of the core wires also lends the cable an added level of security, since an immediate protective disconnection occurs if outside mechanical damage reaches the live wires.
The cable can be produced easily in a single process if the known S/Z binding with alternating direction of twist is used to bind the cores and the wires of the ground wire.